Contribution from descriptive studies to the etiological knowledge of colorectal cancer.

Incidence of colorectal cancer increasing exponentially with age is confirmed but sex-age differences in incidence throughout the large bowel are shown. Observations of incidence within countries indicate that colorectal cancer is a disease of affluent societies. Furthermore, it is hypothesized that a high dietary fat intake leads to an increase in faecal components associated with colon cancer risk.